Preparation of two-dimensional magneto-photonic crystals of bismus substitute yttrium iron garnet materials

Article abstract of DOI:10.1016/j.jmmm.2003.12.256

Porous alumina, which is obtained by anodization of aluminium, has self-ordered pore array. Recently, this ordered pore array structure has been discussed from the viewpoint of the application to two-dimensional photonic crystals (2D-MPC). We prepared porous alumina templates with a pore diameter of 60 nm and thickness of 2 μm. By using these templates as mask, the Bi:YIG film deposited by RF-magnetron sputtering were etched by an Ar ion gun. We were able to fabricate 2D-MPC of Bi:YIG with hole structure.

Full text of DOI:10.1016/j.jmmm.2003.12.256

ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 272–276 (2004) 1690–1691
Preparation of two-dimensional magneto-photonic crystals of
bismus substitute yttrium iron garnet materials
Yoshifumi Ikezawaa,*, Kazuhiro Nishimuraa,1, Hironaga Uchidaa,
Mitsuteru Inouea,b
a Department of Electrical & Electronic Engineering, Toyohashi University of Technology, 1-1 Hibari-Ga-Oka, Tempaku, Toyohashi,
Aichi 441-8580, Japan
b CREST, Japan Science and Technology Corporation, Hongou Tsuna Bldg. 8F, Hongou 6-17-9, Bunkiyou-ku, Tokyo 113-0033, Japan
Abstract
Porous alumina, which is obtained by anodization of aluminium, has self-ordered pore array. Recently, this ordered
pore array structure has been discussed from the viewpoint of the application to two-dimensional photonic crystals
(2D-MPC). We prepared porous alumina templates witha pore diameter of 60 nm and thickness of 2 mm. By using these
templates as mask, the Bi:YIG film deposited by RF-magnetron sputtering were etched by an Ar ion gun. We were able
to fabricate 2D-MPC of Bi:YIG withhole structure.
r 2004 Published by Elsevier B.V.
PACS: 81.07.Àb; 81.16.Dn; 81.16.Àc
Keywords: Porous alumina template; Bismus substitute yttrium iron garnet; Two-dimensional magneto-photonic crystal
In recent years, there has been increasing interest in
the nano-scaled magnetic structures, because of the new
magnetic properties and functionality that it originated
in a nano-scale structure. For example, magneto-
photonic crystals (MPCs) which introduced the periodic
structure of optical wavelengthscaled in the magnetic
garnet material. It is expected that it can realize new
optical magnetic material by controlling the photonic
band gap, which is one of the characteristics. The
photonic crystals (PCs) having a periodic structure are
expected to be used in application for various optoelec-
tronic devices due to their optical properties [1–3]. We
previously reported the numerical and experimental
enhancements of Faraday rotation effect in one-dimen-
sional (1D) MPCs [4]. We proposed two-dimensional
(2D) MPCs which have a stop band in their electro-
magnetic transmission properties. The most common
technique used to fabricate these structures is an electron
beam lithography. However, electron beam lithography
has some drawbacks, such as low throughput due to its
long exposure time, and high cost of equipment. On the
other hand, self-organization materials are being studied
because of high throughput and advantage of industry
viewpoint. Anodic porous alumina has attracted much
interest as a starting material for the fabrication of
functional devices withnano-scales, due to its naturally
occurring nanometer-order channel array structure with
a high aspect ratio [5]. Recently, this ordered pore array
structure has been discussed from the viewpoint of the
application to 2D-PCs [6].
In this study, we fabricated anode oxidation porous
alumina templates. By using these templates as a mask,
we tried to fabricate 2D-MPCs of a bismus substitute
yttrium iron garnet (Bi:YIG) film.
Self-organization porous alumina withperiodic struc-
tures was fabricated by anodization of Al sheet in oxalic
acid, and nanoscale magnetic structures fabricated using
alumina template. Al plate was degreased and the
chemical polished by a mixture solution of phosphoric
acid and nitric acid. The anodization of Al plates was
*Corresponding author. Tel.: +81-532-44-6749;
fax: +81-532-44-0120.
E-mail addresses: yike@maglab.eee.tut.ac.jp (Y. Ikezawa),
nishimura@eee.tut.ac.jp (K. Nishimura).
1 Also for correspondence.
0304-8853/$ - see front matter r 2004 Published by Elsevier B.V.
doi:10.1016/j.jmmm.2003.12.256

ARTICLE IN PRESS
Y. Ikezawa et al. / Journal of Magnetism and Magnetic Materials 272–276 (2004) 1690–1691
1691
Fig. 1. SEM observation on the cross-section of the porous
alumina template.
Fig. 3. SEM observation of the hole-structured Bi:YIG film.
utilized as the mask that fabricated nanoscale hole
structures.
The Bi:YIG films were prepared by RF-magnetron
sputtering. Fig. 2 shows X-ray diffraction patterns of
these films. Although these films are amorphous in the
as-deposited state, they are crystallized to garnet
structure by annealing at 700ꢀC for 20 min.
By using the mask of the porous alumina template, we
etched the Bi:YIG film by an Ar ion beam gun. As
shown in Fig. 3, we confirmed the hole-structured
Bi:YIG film.
Porous alumina templates prepared by pretexturing
Al plates nano-indented by a SiC mold, which has an
arranged array of convexes formed using conventional
electron beam lithography, were filled by uniformly
sized cells [7]. By using these templates, we will achieve
fabricating the complete defect-free 2D-MPCs of the
Bi:YIG or 2D-MPCs controlled defect.
This study has been financially supported in part by a
Grant-in-Aid for Scientific Research(A) (2) (#14205045)
from the Ministry of Education, Culture, Sports, Science
and Technology.
Fig. 2. XRD pattern of prepared films.
achieved in oxalic acid solution under a constant
voltage. Porous alumina withhighordered pore array
was fabricated by appropriate voltage and anodization
time. It is known that porous alumina has a random
pore array in the early growth. Porous alumina which
has a straight hole was fabricated by a two-step
anodizing process and expansion of the pore diameter
was carried out by the pore-widening treatment in
NaOH solution. Fig. 1 shows a straight hole porous
alumina withpore diameter 60 nm and thickness 2 mm.
We obtained pure porous alumina templates by taking
off Al plates. These porous alumina templates were
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